Hot tops with exothermic inserts



Oct. 30, 1962 E. MARBURG HOT ToPs WITH ExoTHERMIc INsERTs Attorney Oct. 30, 1962 E. MARBURG 3,060,533

HOT TOPS WITH EXOTHERMIC INSERTS Filed sept. 16, 1959 s sheets-sheet 2 5 26` PILE: El 42 ,f2s 207 A lar/ley Oct. 30, 1962 E. MARBURG '3,060,533

HOT TOPS WITH EXOTHERMIC INSERTS Filed Sept. 16, 1959 3 Sheets-Sheet 3 v /lv vE/v ron EDGAR MARBURG A Home! x. r. `4.|.... u... u. .P l.. A

United States Patent tice 3,060,533 Patented Oct. 30, 1962 3 060 533 HOT TGPS WITH XTHERMIC INSERTS Edgar Marburg, 1287 Prospect Road, Pittsburgh 27, Ia. Filed Sept. 16, 1959, Ser. No. 840,268 9 Claims. (Cl. 22-147) This invention relates to hot tops with exothermic inserts and more particularly to such hot tops for use with a mold for casting metal. The most common of such hot tops are those used in connection wtih ingot molds for casting steel ingots. The purpose of a hot top is to provide a storage space for maintaining the molten metal fluid at the top of the casting for a long period of time so as to compensate for shrinkage of the main portion of the metal as it solidies. This is also necessary when casting rolls and other relatively large objects. The present application is a continuation-in-part of my co-pending application Serial No. 30,684, tiled April 24, 1958, now abandoned, which in `turn is a continuation-in-part of my co-pending application Serial No. 636,146, filed January 24, 1957, now Patent No. 2,914,825, ydated December 1, 1959.

There are several Vtypes of existing hot tops which contain exothermic material; the entire hot top being made of eXothermic material, a one-piece clay hot `top lined with exothermic material, duplex slabs comprising an eXothermic inner layer and a refractory outer layer which are hung along two sides only of large molds, an exothermic lining provided in a recess in the upper end of a mold, and an exothermic lining placed in a cast iron housing. All of these types `of hot tops have a joint between the hot top and the mold where it is diflicult Ito obtain a good seal to prevent leakage of metal which causes ns and hanger cracks in the inogt. It is diicult =to keep the duplex slabs from floating upward in the liquid metal. In each of these hot tops the amount of exothermic material necessary is relatively large and since this material is expensive the use of these hot tops has been conned principally to alloy steels. The cost of construction of the hot tops is also high. It has also vbeen proposed to provide a hot top in which the exotherrnic material is embedded in the wall of the hot top intermediate its height with the only opening being vent holes to vthe outside of the hot top. This has several disadvantages. Most eX- othermic materials commonly used -require a temperature of 600 F., to ignite. This means that the inside refractory Wall of the hot top would have to be heated to 600 F. before the exothermic layer would ignite. To attain such a high temperature at the far side of a wall of insulating refractory material a considerable amount of heat would have to be abstracted from the sinkhead metal, so that a comparatively thick metal shell would be soliditied before the exothermic material would even be ignited. The inner refractory wall could, of course, be made thinner, and the above comments would still apply, but Vthe solidified wall would not be quite so thick. In other words there is no advantage to having the exothermic insert embedded unless a solidified shell is desired so that the ingot may -be picked up by its sinkhead. If it is desired to keep the sinkhead metal liquid and to prevent a metal shell from forming, it is preferable to place the eXothermic material on the inside face next to the metal. The embedded exothermic layer near midheight in a hot top wall would be entirely ineffective in supplying heat to the vbase portion of the hot top. This last-to-freeze portion is the most critical portion of a hot top in regard to its efficiency and performance. It is important that the metal be kept liquid here as long as possible, both to avoid pipe and segregation in the ingot body, and to minimize the sinkhead volume. While the application of exothermic inserts at other portions of the hot top may be of limited value, they cannot provide the most effective results. Other ldisadvantages of the present use of eX- othermic material is that careful pouring is required, there is difficulty in stripping the ingots, the heat evolved may produce internal segregation in the upper portion of the ingot, the efficiency of utilization of the exothermic material is poor and thereis the hazard of the exothermic material absorbing moisture during storage of the hot top.,

It is therefore an object of my invention to proivde a hot top which is so `constructed that there is excellent utilization of the exotherrnic material.

Another object is to provide such a hot top which has a small sinkhead volume relative to the ingot volume.

Still another object is to provide such a hot top which enables the ingots poured therewith to be easily handled.

These and other objects will be more apparent after referring to the following specication and attached drawings, in which:

FIGURE 1 is a plan view of a sectional hot top assembled on an ingot mold;

FIGURE 2 is an enlarged plan view showing the joint between an end and side slab;

FIGURE 3 is an elevation of the side slab looking toward its inner face with parts cut away;

FIGURE 4 is an end view of the slab of FIGURE 3 with parts cut away;

FIGURE 5 is a top plan view of the slab of FIG- URE 3;

FIGURE 6 is a view, similar to FIGURE 3, showing the end slab;

FIGURE 7 is ran end view of the slab of FIGURE 6 with parts cut away;

FIGURE 8 is a top plan view of the slab of FIG- URE 6;

FIGURE 9 is a View in elevation showing the assembled slabs on a -mold section and looking inwardly from the outer side of an end slab;

FIGURE 10 is a sectional view showing my invention applied tothe mold used in the casting of a steel roll;

FIGURE l1 is a fragmentary view, similar to FIG- URE 10, showing another embodiment of my invention; and

FIGURE 12 is a fragmentary view, similar to FIG- URE 10, showing still another embodiment of my invention.

Referring more particularly to the drawings, reference numeral 2 indicates the top of -a rectangular big-end-up mold. The hot top shown consist-s of two side slabs 4 and two end slabs 6. Each side slab 4has a substantially vertical smooth inner face 8 while its outer face has a `depressed upper portion 10 and a vertical lower portion 12, which ts the lrnold wall, whether plain or corrugated. The bottom of the inner face 8 is rounded at 14. A plurality of holes 16 are provided in the wall of the slab 4 for a purpose which will appear later. The upper portion of the ends of the slabs 4 are preferably cut away at 18 so that they are wider at Ithe bottom than at the top. A generally vertical groove 20 is provided in the inner face of slab 4 a short distance from each end thereof. The bottom of the groove 20 tapers downwardly and inwardly at 22 for a purpose which will appear later. The inner side wall 24 of each groove 2li is vertical for the most of its length, but slopes outwardly in 'a downward 4direction at its lower end 25 so that the groove is narrower at the bottom than at the top. Outer side wall 24 of groove 20 is substantially vertical. A generally vertical slot 26 is provided in the upper louter side of slab 4 adjacent each of its ends.

Each end slab 6 has =a generally vertical inner face 28 and a depressed portion 30 in its outer face. The contour of the lower portion of the outer face matches the 3 mold wall. The bottom of the inner face 28 is rounded at 31. Each end of the slab 6 has a generally vertical tongue 32 which has tapered sides 34. The width of the upper portion of tongue 32 is less than the width of the upper parallel portion of the groove 20. The lower portion of the front face of tongue 32 has a tapered portion 35 which is of the same slope, but `slightly closer to its base than tapered portion 22 of slab 4. The inner side face of the tongue 32 is tapered at its lower end to provide a wedge surface 32' of the same slope but slightly nearer its base than the tapered portion 25 of slab 4. Portion 36 of the end face is normal to the Vface 28. Portion 3S of the end face slopes inwardly toward the other end face of slab 6. The height of the tongue 32 adjacent portion 36 is slightly greater than the depth of groove 20 and the height of the opposite side of the tongue 32 is less than the depth of the groove 20. A generally vertical slot 40, similar to slot 26, is provided on the `upper outer face of slab 6 adjacent each end. A vertical slot `42 open at the bottom edge is provided in the middle portion of the walls of side slabs 4 and a similar slot 44 is provided in the end slabs 6. The parts so far described except ifor minor differences are the same as those shown in my above mentioned Patent No. 2,914,825.

The invention in the present application relates to the addition of exothermic inserts 46 and 47 in the bottom of slots 42 and 44, respectively, and the provision of vent holes 50 and 52 extending outwardly from the top of slots 42 and 44, respectively. The slots 42 and 44 extend upwardly from the bottom edge to within about four inches of the top of the slabs. The slots may be of uniform width throughout their height, but are preferably narrower at their upper end as shown. The exothermic material may extend upwardly from the bottom of slots 42 and 44 to any desired height. Any portion of the slot not filled with exothermic material may be open or may contain a layer of combustible material such as a strip of corrugated cardboard arranged with its corrugations vertical. The exothermic material from which the inserts are made is well known. A composition which has proved satisfactory includes 30% aluminum powder, 5 to 10% barium nitrate, 5% manganese dioxide, 5% iron oxide, 40 to 45% aluminum grog (oxides and silicates), l to 2% sodium- `and/or aluminum iluorides, and 3 to 5% of a binder such as clay plus sulfite lyes. The above percentages are by weight and after mixing the ingredients together water is added and the material molded into any desired shape. It is preferably hardened by heating to between 100 to 400 F. for one to three hours. The heat is generated by the reaction between the aluminum and the oxidizing agents which are the barium nitrate, manganese dioxide and iron oxide, and also the reaction between the aluminum and the air. The rate of burning is controlled by the amount of the several oxidizing agents present and the aluminum grog prevents too rapid burning. The uorides trigger the initial ignition and insure continuous burning to completion. The hot: top proper may be made of reclay or of a bonded sand mix consisting of sand mixed with a liquid binder in which phenol resin is the principal ingredient or a sodium silicate binder. The invention may also be utilized with one-piece hot tops which t into the mold as a unit.

To assemble the hot top on the -mold 2, a one-fourth inch round steel pin 54 is placed in each of a pair of holes 16 at `any of three levels (depending upon the height of ingot desired) and the side slabs 4 are placed on opposite sides of `the mold 2 -with the pins 54 resting on top of the mold as best shown in FIGURE 9. The end slabs 6 are then inserted between the side slabs 4 with the tongue 32 in the grooves 20. Because groove 20 is wider than tongue 32 in its parallel upper portion, the tongues 32 will pass readily into the grooves 20. When the slabs 6 reach the point where beveled faces 22 and 35 are in engagement, the outer sides of the side slabs 4 are forced towards the mold wall. At the same depth the lower bevels 25 and 32 contact each other, and end slabs 6 are forced outwardly towards the mold wall. With clearances allowed, the slight difference in height of bevelled faces 22 and 35 and corresponding bevels 25 and 32' results lin the tops of slabs 4 and 6 being aligned when a tight fit is secured. When the top of end piece 6 is level with the top of side piece 4, the side face 34 of tongue 32 contacts the outer face 24' of groove 20; hence the end slab 6 cannot drop below the level of the side slab 4. After the four slabs are assembled, a generally U-shaped spring clip 58 is forced downwardly across each joint between the slabs with its legs in the slots 26 and 40. Alternately wood wedges may be driven between the side slabs and the mold near the end of each side slab. The above manner of assembly is essentially that shown in my above mentioned Patent No. 2,914,825.

When the exothermic material exposed at the bottom edge of each slab is ignited by the heat of the steel it burns and develops a temperature of about 3000 F, for approximately ve minutes. The gases from the burning material pass upwardly through the slots 42 and 44 and escape through vent holes 50 and 52. Even when using only about 17% as much exothermic material as used in other types of hot tops sound ingots have been produced ywith only 8.5% sinkhead volume. Essentially all of the heat of the burning material is used to heat the hot top on both sides of the slots and since Ithe width of the exothermic material in the slot is greater than the thickness of exothermic liners it burns for a longer time and develops a high temperature over a longer period of time than the conventional exothermic hot top. The exothermic inserts are located at the lower portions of the slabs where it is most important that the heat in the sinkhead be conserved. This is the last-to-freeze portion of the sinkhead; hence the most critical to keep liquid as long as practicable to insure against pipe in the ingot and to permit segregates to rise freely into the sinkhead. Since the inside wall of the hot top is not heated instant- 1y a wall of metal solidifies initially around the inside of the hot top so that big-end-up ingots may be picked up by the soaking pit crane tongs in a conventional manner.

FIGURE 10 shows my invention as applied to the casting of steel rolls as shown on pages 560 to 563 of The Making, Shaping and Treating of Steel, Sixth Edition. As shown therein a steel ask 60 is filled with sand 62 having chills 64 embedded therein at the body portion of the roll. The upper portion of the sand forms a hot top in which is poured .the sinkhead metal 66. A sprue 68 extends upwardly through the sand to a gate 70. According to my invention I provide a vertical slot 72 which extends around the wall of the hot top at a shallow depth below the inside face. The bottom of the slot 72 has a peripheral opening 74 therein extending to the inner surface of the hot top so as to be contacted by the molten met-al. Vent holes 76 are provided at the top of slots 72. An exothermic insert 78 is provided in the bottom of the slot 72. The slot 72 above insert 78 is preferably narrower than the insert. Instead of an open slot, a combustible material such as corrugated cardboard (with the corrugations vertical) may be placed in slot 72. The operation of this hot top is essentially the same as that of the hot tops previously described. It will be noted that the drawing is illustrative only since the metal M will not have reached the position shown before ignition of the exothermic material starts. It will be understood that the exothermic material may extend only part way up in the slot 72 or it may completely lill it.

In the embodiment of my invention shown in FIGURE 11 a slot 80 is provided which extends downwardly almost to the roll body where an opening 82 is provided.

In the embodiment of my invention shown in FIGURE 12 a slot S6 is provided which is similar to slot 80. lHowever, the bottom opening is omitted and an opening 88 is provided at the top of the slot. This embodiment reduces the amount of heat applied next to the roll neck, so that a hard chill surface may form here. The exothermic material in these hot tops enables sound castings to be produced with considerably less sinkhead volume than now used. It eliminates padding, that is increasing the neck vsection to insure proper feeding, so that less machining of the casting is necessary.

In each of the embodiments shown the exothermic material may be introduced as loose material or as a premolded duplex insert that comprises the exothermic layer plus the inner wall.

While several embodiments of my invention have been shown and described, it will be `apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. =A hot top for use with a mold for casting metal cornprising a refractory body member having generally vertical inner and outer walls, an insert of exothermic material located between said inner and outer walls, said insert extending generally vertically around a substantial length of the periphery of said hot top and with a minor portion thereof extending to that surface `of said body member which receives .said metal.

2. A hot top for use with a mold for casting metal comprising a refractory body member having generally vertical inner and outer Walls, said body member having a generally vertical slot therein between said inner and outer walls extending upwardly to a position below the top of said body member, said slot extending around a substantial length of the periphery of said hot top, said body member having a peripheral opening therein from said slot to that surface of said body member which receives said metal, the height of said slot being substantially greater than `that dimension of said opening generally transverse to its peripheral dimension, and an insert of exothermic material in said slot adjacent said opening.

3. A hot top for use with a mold for casting metal comprising a refractory body member having generally vertical inner and outer walls, said body member having a generally vertical slot therein between said inner and outer walls extending upwardly to a position below the top of said body member, said slot extending around a substantial length 4of the periphery of said hot top, said body member having la peripheral opening from the bottom of said slot to ythat surface of said body member which receives said metal, the height of said slot being substantially greater than that dimension of said opening generally transverse to its peripheral dimension, and an insert of exot-hermic material in said slot adjacent said opening.

4. A hot top for use with -a mold for casting metal comprising a refractory body member having generally vertical inner and outer walls, said body member having a generally vertical Slot therein between said inner and outer walls extending upwardly to a position below the top of said body member, said slot extending around a substantial length of the periphery of said hot top, said body member having a peripheral opening from the top of said slot to that surface of said body member which receives said metal, the height of said slot being substantially greater than that dimension of said opening generally transverse -to its peripheral dimension, and an insert of exothermic material in said slot adjacent said opening.

5. A hot top for use with a mold for casting metal comprising a refractory body member having generally vertical inner and outer Walls, said body member having a generally vertical slot therein between said inner and outer walls extending upwardly to a position below the top of said body member, said slot extending around a substantial length of the periphery of 4said hot top, said body member having a peripheral opening from the ,bottom of said slot to that surface of said body member which receives said metal, said body member having an opening from the top of said slot to that surface of said body member which receives said metal, the height of said slot being substantially ygreater than that dimension of each of said openings generally transverse to its peripheral dimension, 'and an insert of exotherm-ic material in said slot adjacent said openings.

6. A sectional hot top for insertion within the walls of a mold for casting metal comprising a first pair of refractory slabs supported on said mold in spaced relationship, a second pair of refractory slabs located between and in abutting relationship with said iirst pair of slabs, means on said slabs for Wedging them against the mold wall, each of said slabs having a generally vertical slot therein extending upwardly to a position below the top thereof, said slot having a peripheral opening to that surface of the slab which receives said metal, the height of said slot being substantially greater than lthat dimension of said opening generally transverse to its peripheral dimension, and an insert of exothermic material in said slot adjacent said opening.

7. A sectional hot top according to claim 6 in which the opening is in the bottom of the slab.

8. A sectional hot top according to claim 6 in which the opening is from the top of the slot.

9. A sectional hot top according to claim 7 in which there is an opening from the top of the slot.

References Cited in the le of this patent UNITED STATES PATENTS 2,390,500 Charman etal Dec. 11, 1945 2,821,000 Nouveau Jan. 28, 1958 2,841,843 Nouveau July 8, 1958 2,914,825 Marburg Dec. 1, 19'59r 

1. A HOT TOP FOR USE WITH A MOLD FOR CASTING METAL COMPRISING A REFACTORY BODY MEMBER HAVING GENERALLY VERTI- 